DESCRIPTION: HIV-1 infection is the result of a complex interplay of virologic and immunologic factors. The immunologic determinants of HIV infection have received less attention than other factors and the immunologic determinants in pregnancy and infancy even less. Understanding immune function in pregnancy and infancy is complicated by the profound physiologic changes associated with these conditions. Therefore, The investigators will examine the immunologic determinants of HIV infection in the uninfected and infected pregnant women and their infants. The specific aims will be to (1) define the immunologic changes in pregnancy with and without HIV infection, and (2) define the immunologic changes in infancy with and without HIV infection. The changes will be examined in the context of immunologic determinants of HIV infection that include (a) nonspecific immunomodulatory factors of pregnancy and immaturity (e.g. immunoregulatory cytokines, lymphocyte and monocyte phenotypes), (b) proinflammatory factors (e.g. TNF(); (3) anti-HIV immunity (e.g. CD8 anti-HIV activity); and (4) mechanisms of destruction of immune cells (e.g. apoptosis). Specific hypotheses addressing these aims will be examined. The studies will be carried out using fresh samples from uninfected and infected pregnant and postpartum women from their infants. Additional studies will utilize cryopreserved samples from WITS (Women and Infants Transmission Study). The studies will increase the knowledge of the immune system in this special group of subjects and assist in the development of preventive and therapeutic modalities.